A pneumatic valve arrangement is disclosed in DE 10 2009 029 968 A1 by the same Applicant. In this valve arrangement, the insert which is secured to the housing and the plate valve are located in a lower housing portion and the relay valve piston is located coaxially relative thereto in an upper housing portion. This upper housing portion is connected to the lower housing portion in a sealed manner and has to be orientated in the most precise manner possible with respect to the coaxially arranged plate valve and the relay valve piston in order to ensure the functionality of the valve arrangement. The insert which is secured to the housing is sub-divided in the housing by means of a securing ring which is fixed in position in a groove in the lower housing portion.
The supply of control pressure to the operating chamber is carried out by means of obliquely extending holes or channels in the lower housing portion and in the upper housing portion. The ventilation of the operating chamber to the environment is carried out via a central hole in the relay valve piston and by means of a noise damper whose housing is fixed to the upper housing portion by means of a clip-fit connection. A first embodiment of the known valve arrangement comprises only one relay valve. Another embodiment of this valve arrangement has two relay valves which are arranged in a mirror-symmetrical and coaxial manner relative to each other. This latter embodiment with two relay valves may have in the ventilation path a noise damper to which both relay valves are connected, or each of the relay valves is connected to a separate noise damper. Each relay valve is acted on with control pressure by means of separate obliquely extending channels in the housing.
The relay valve or the two relay valves may supply at least one pneumatically actuatable brake cylinder of a pneumatically or electro-pneumatically actuatable braking system with compressed air. The control pressure may be a pressure which is controlled pneumatically, for example, by means of a brake pedal, controlled pressure or a pressure which is controlled electro-pneumatically, for example, by means of solenoid valves. The relay valve or the relay valves provide(s) the control pressure reinforced with quantities of air for the brake cylinder which, in response to an increase of the pressure, presses a brake lining against a brake disc which is arranged on a wheel shaft of a motor vehicle and consequently brakes the wheel or the motor vehicle. The relay valve in this instance shortens the response time of the brake or the period of time until the beginning of a braking operation by means of rapid air supply to the brake cylinder. In addition, the relay valve or relay valves enable(s) rapid ventilation of the brake cylinder(s).
This known valve arrangement has been proven to be advantageous in particular in terms of its operating method, but requires a complex processing of the compressed air channels which are constructed as oblique holes, a mechanical processing of the lower housing portion and the upper housing portion in all directions for a precise orientation of the upper housing portion with respect to the lower housing portion, in particular as a result of the arrangement of the relay valve piston running face in the upper housing portion and the remaining movable components in the lower housing portion so that the interfaces extend towards each other and have to be sealed. During assembly, there are different assembly directions so that the assembly, whether carried out by hand or by a machine, is complex and requires a relatively significant amount of time. Furthermore, the coupling of one or more solenoid valves which are required cannot readily be standardised in such a manner that different solenoid valve units from different manufacturers can be coupled to the relay valve component. Finally, there is also limited flexibility for construction of variants, for example, for single-channel systems or dual-channel systems, which may or may not be provided with redundancy connections and which enable a complete circuit separation.
Redundancy connections are required for safety reasons when the valve arrangement is controlled by means of an electronic motor control unit. In this instance, in the event of a failure of the electronic motor control unit, a redundancy pressure which is supplied by a pedal-controlled brake value transmitter is supplied directly to the relay valve(s).